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1、氨 基 酸 代 谢 Metabolism of Amino Acids,第 七 章,CHAPTER 7,Section 5,Metabolism of Individual Amino Acids,个别氨基酸的代谢,一、Decarboxylation of amino acids generates special amines,Decarboxylation (脱羧基作用),( 氨基酸脱羧酶),Amino acids,Amines,RCH2NH2,+ CO2,(磷酸吡哆醛),Amino acid decarboxylase,Phosphopyridoxal,氨基酸的脱羧基作用产生特殊的胺类化
2、合物,胺类,氨基酸,Coenzyme pyridoxal phosphate磷酸吡哆醛,Amines,Aldehyde,Carboxlic acids,Monoamine oxidase,胺类,醛类,羧酸类,（一） -aminobutyric acid, GABA (-氨基丁酸) is generated from glutamate catalyzed by glutamate decarboxylase 谷氨酸经谷氨酸脱羧酶催化生成-氨基丁酸(GABA),GABA is a kind of inhibitive neurotransmitter which has inhibitive f
3、unction to central nerve system.,L- 谷氨酸脱羧酶,L-谷氨酸,-氨基丁酸,GABA是抑制性神经递质，对中枢神经有抑制作用。,（二）Decarboxlation of histidine catalyzed by histidine decarboxlase generates histamine 组氨酸经组氨酸脱羧酶催化生成组胺,Histamine is an intensive vasodilator which can increase the permeability of blood capillary and stimulate the secre
4、tion of pepsinogen and gastric acid.,Histidine decarboxlase,组氨酸脱羧酶,L-组氨酸,组胺,组胺是强烈的血管舒张剂，可增加毛细血管的通透性，还可刺激胃蛋白酶原及胃酸的分泌。,（三）5-hydroxytryptamine, 5-HT (5-羟色胺 ) is generated from tryptophane via 5-hydroxytryptophan 色氨酸经5-羟色胺酸生成5-羟色胺,5-HT serving as neurotransmitter has inhibitive function in brain , and i
5、t also plays a role in contraction of blood vassele in peripheral tissues. 5-HT在脑内作为神经递质起抑制作用；在外周组织有收缩血管的作用。,5-hydroxytryptophan,5-HT,Tryptophan hydroxylase,5-hydroxytryptophan decarboxylase,CO2,Tryptophane,CH2CHCOOH NH2,HO,5-羟色氨酸,色氨酸,5-羟色氨酸脱羧酶,色氨酸羟化酶,5-羟色胺,（四）Some amino acids can produce polyamines
6、 through decarboxylation 某些氨基酸的脱羧基作用可产生多胺类,Onithine decarboxylase (鸟氨酸脱羧酶),Ornithine,Putrescine,S-adenosyl methionine (SAM ),Decarboxylated SAM,CO2,SAM decarboxylase,CO2,Spermidine (精脒 ),丙胺转移酶,5-methyl-S-adenosine,Propylamine decarboxylase (丙胺转移酶),Spermine (精胺 ),Polyamines are important substances r
7、esponsible for regulation of cell growth. 多胺是调节细胞生长的重要物质。,Propylamine transferase,鸟氨酸,腐胺,5-甲基-硫-腺苷,S-腺苷甲硫氨酸,SAM脱羧酶,脱羧基SAM,二、The catablism of some amino acids can generate - One carbon unit ( 一碳单位),Concept of one carbon unit 一碳单位的定义,（一）Tetrahydrofolic acid acts as a carrier of one carbon unit and par
8、ticipates the metablism of one carbon unit,The groups containing one carbon atom generated from the catabolism of some amino acids is called one carbon unit (一碳单位).,某些氨基酸在分解代谢中产生一碳单位,四氢叶酸作为一碳单位的运载体参与一碳单位代谢,某些氨基酸在分解代谢过程中产生的含有一个碳原子的基团，称为一碳单位(one carbon unit)。,Types of one carbon unit,methyl (甲基 ) -CH3
9、 methylene (甲烯基 ) -CH2- methenyl (甲炔基 ) -CH= formyl (甲酰基 ) -CHO formimino (亚胺甲基 ) -CH=NH,一碳单位的种类,维生素B11（叶酸,Folic Acid) 结构,FH4 is a carrier of one carbon unit,FH4 携带一碳单位的形式,叶酸在5、6、7、8位加上四个氢，生成四氢叶酸（FH4），四氢叶酸是一碳单位的载体，传递一碳单位。 它在核酸和蛋白质的代谢中具有重要意义。,5,6,7,8- tetrahydrofolic acid (FH4),Structure of tetrahydr
10、ofolic acid,四氢叶酸的结构,Generation of FH4,FH4的生成,FH4 is a carrier of one carbon unit,（One carbon unit usually links to the N5 or N10 position of FH4）,FH4 携带一碳单位的形式,一碳单位通常是结合在FH4分子的N5、N10位上,The one carbon unit is generated from the catabolism of serine、glysine and histidine.,（二） Different one carbon unit
11、s generated from amino acids can undergo interconversion,由氨基酸产生的一碳单位可相互转变,一碳单位主要来源于丝氨酸、甘氨酸、组氨酸及色氨酸的分解代谢,丝氨酸,甘氨酸,组氨酸,色氨酸,一碳单位的来源：肝胆阻塞死 （甘氨酸、蛋氨酸、组氨酸、色氨酸、丝氨酸）,The interconversion of different one carbon units,一碳单位的互相转变,（三）The main function of one carbon unit is the involvement of synthesis of purine an
12、d pyrimidine 一碳单位的主要功能是参与嘌呤、嘧啶的合成,N10-CHO-FH4 and N5,N10=CH-FH4 provide C2 and C8 for purine synthesis respectively. N5, N10-CH2-FH4 provides methyl group for thymidine synthesis . N10-CHO-FH4与N5,N10=CH-FH4分别为嘌呤合成提供C2与C8，N5,N10-CH2-FH4为胸腺嘧啶核苷酸合成提供甲基。 Make the connection between the metabolism of ami
13、no acids and nucleotides. 把氨基酸代谢和核酸代谢联系起来。,Synthesis of nucleotides,9,8,7,6,5,4,3,2,1,N5,N10-CHO-FH4,N,C,N,C,C,C,N,C,N,N5,N10-CH2-FH4,N10-CHO-FH4,formyl,methylene,三、The interrelationship of the metabolism of different sulfur-containing amino acids,Cystine (胱氨酸),Methionine (甲硫氨酸),Cysteine,(半胱氨酸),含硫氨基
14、酸的代谢是相互联系的,含硫氨基酸,（一）Methionine participates in transmethylation,1、Transmethylation of methionine is related with methionine cycle 甲硫氨酸转甲基作用与甲硫氨酸循环有关,Adenylase (腺苷转移酶),PPi+Pi,+,Methionine,ATP,S-Adenosylmethionine (SAM),Adenine,Adenine,甲硫氨酸参与甲基转移,甲硫氨酸,S腺苷甲硫氨酸,SAM中的甲基是高度活化的，称活性甲基，SAM称为活性蛋氨酸。,(甲基转移酶),RH
15、,RCH3,SAM,(S-腺苷同型半胱氨酸),(同型半胱氨酸),SAM is a direct donor of methyl group,Methyltransferases,Homocysteic acid,S- adenosyl homocysteine,Adenosine,Adenine,Adenine,SAM为体内甲基的直接供体,腺苷,S腺苷甲硫氨酸,Methionine cycle (甲硫氨酸循环),Methionine,S-adenosyl homocysteic acid,S-adenosyl methionine,Homocysteic acid,FH4,N5CH3FH4,N
16、5CH3FH4 Methyl transferase;,(VitB12),H2O,Adenosine,RH,ATP,PPi+Pi,R,-CH3,甲硫氨酸,S-腺苷甲硫氨酸,S-腺苷同型 半胱氨酸,腺苷,转甲基酶,同型半胱氨酸,此循环的生理意义在于蛋氨酸分子中甲基可间接通过N5-CH3-FH4由其它非必需氨基酸提供，以防蛋氨酸的大量消耗。 N5-CH3-FH4同型半胱氨酸甲基转移酶的辅酶是维生素B12。维生素B12缺乏会引起蛋氨酸循环受阻。临床上可以见到维生素B12缺乏引起的巨幼红细胞性贫血。,2、Methionine provides methyl group for the synthesis of creatine 甲硫氨酸为肌酸合成提供甲基,Creatine and creatine phosphate are important compounds f
